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- Corrigendum to "Use of solid phase extraction for the sequential injection determination of alkaline phosphatase activity in dynamic water systems"Publication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O.S.S.
- Use of Solid Phase Extraction in a Sequential Injection System for the Determination of Alkaline Phosphatase Activity in Plant RootsPublication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O. S. S.
- Sistemas de fluxo para a monitorização de nutrientes em águas de transição e costeirasPublication . Mesquita, Raquel; Santos, Inês C.; Bordalo, Adriano A.; Rangel, António O. S. S.
- Seasonal monitoring of inland bathing waters using a sequential injection method as a fast and effective tool for nutrient quantification (N : P)Publication . Mesquita, Raquel B. R.; Machado, Ana; Santos, Inês C.; Bordalo, Adriano A.; Rangel, António O. S. S.In this work, an expedite flow method for the combined determination of major nutrients, nitrogen base ions (nitrate, nitrite and ammonium) and phosphate, is described for seasonal monitoring of inland bathing waters. Individual determinations were adapted and comprised within the same manifold to attain a comprehensive assessment of the environmental status of natural waters. The multiparametric determination was performed to explore the features of a sequential injection analysis technique yielding a real-time assessment of various parameters and effective in-line sample handling. The sequential injection multiparametric method enabled the determination within the ranges: 15.0-150 mu M nitrate; 0.15-5.00 mu M nitrite; 1.00-60 mu M ammonium; and 0.2-30 mu M phosphate. The determination rates provided a full nutrient analysis within 7 minutes, an overwhelming improvement in relation to the individual determination of each parameter. The described method was successfully applied to seasonal monitoring of six inland bathing waters dealing in-line with sample variability.
- Multiparametric sequential injection system for carbon speciation in bathing watersPublication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O. S. S.
- Iodine speciation in coastal and inland bathing waters and seaweeds extracts using a sequential injection standard addition flow-batch methodPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Bordalo, Adriano A.; Rangel, António O. S. S.The present work describes the development of a sequential injection standard addition method for iodine speciation in bathing waters and seaweeds extracts without prior sample treatment. Iodine speciation was obtained by assessing the iodide and iodate content, the two inorganic forms of iodine in waters. For the determination of iodide, an iodide ion selective electrode (ISE) was used. The indirect determination of iodate was based on the spectrophotometric determination of nitrite (Griess reaction). For the iodate measurement, a mixing chamber was employed (flow batch approach) to explore the inherent efficient mixing, essential for the indirect determination of iodate. The application of the standard addition method enabled detection limits of 0.14 µM for iodide and 0.02 µM for iodate, together with the direct introduction of the target water samples, coastal and inland bathing waters. The results obtained were in agreement with those obtained by ICP-MS and a colorimetric reference procedure. Recovery tests also confirmed the accuracy of the developed method which was effectively applied to bathing waters and seaweed extracts.
- Iodine specification in bathing waters and seaweed using a si flow-batch standard addition methodPublication . Santos, Inês C.; Mesquita, Raquel; Bordalo, Adriano A.; Rangel, António O.S.S.
- Sequential injection methodology for carbon speciation in bathing watersPublication . Santos, Inês C.; Mesquita, Raquel B. R.; Machado, Ana; Bordalo, Adriano A.; Rangel, António O. S. S.A sequential injection method (SIA) for carbon speciation in inland bathing waters was developed comprising, in a single manifold, the determination of dissolved inorganic carbon (DIC), free dissolved carbon dioxide (CO2), total carbon (TC), dissolved organic carbon and alkalinity. The determination of DIC, CO2 and TC was based on colour change of bromothymol blue (660 nm) after CO2 diffusion through a hydrophobic membrane placed in a gas diffusion unit (GDU). For the DIC determination, an in-line acidification prior to the GDU was performed and, for the TC determination, an in-line UV photo-oxidation of the sample prior to GDU ensured the conversion of all carbon forms into CO2. Dissolved organic carbon (DOC) was determined by subtracting the obtained DIC value from the TC obtained value. The determination of alkalinity was based on the spectrophotometric measurement of bromocresol green colour change (611 nm) after reaction with acetic acid. The developed SIA method enabled the determination of DIC (0.24-3.5 mg C L-1), CO2 (1.0-10 mg C L-1), TC (0.50-4.0 mg C L-1) and alkalinity (1.2-4.7 mg C L-1 and 4.7-19 mgC L-1) with limits of detection of: 9.5 mu g C L-1, 20 mu g C L-1, 0.21 mg C L-1, 0.32 mg C L-1, respectively. The SIA system was effectively applied to inland bathing waters and the results showed good agreement with reference procedures.
- Use of solid phase extraction for the sequential injection determination of alkaline phosphatase activity in dynamic water systemsPublication . Santos, Inês C.; Mesquita, Raquel B.R.; Bordalo, Adriano A.; Rangel, António O.S.S.In this work, a solid phase extraction sequential injection methodology for the determination of alkaline phosphatase activity in dynamic water systems was developed. The determination of the enzymatic activity was based on the spectrophotometric detection of a coloured product, p-nitrophenol, at 405 nm. The p-nitrophenol is the product of the catalytic decomposition of p-nitrophenyl phosphate, a noncoloured substrate. Considering the low levels expected in natural waters and exploiting the fact of alkaline phosphatase being a metalloprotein, the enzyme was pre-concentrated in-line using a NTA Superflow resin charged with Zn2þ ions. The developed sequential injection method enabled a quantification range of 0.044–0.441 unit mL 1 of enzyme activity with a detection limit of 0.0082 unit mL 1 enzyme activity (1.9 mmol L 1 of pNP) and a determination rate of 17 h 1. Recovery tests confirmed the accuracy of the developed sequential injection method and it was effectively applied to different natural waters and to plant root extracts.
- Use of a sequential injection system to monitor the efficiency of a constructed wetlandPublication . Mesquita, Raquel B. R.; Santos, Inês C.; Calheiros, Cristina S. C.; Bordalo, Adriano A.; Castro, Paula M. L.; Rangel, António O. S. S.